A Datum Feature Is Not a Datum (#225)
(In accordance with Y14.5M-1994 standard)
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First, it is not considered good practice to have such a large flatness tolerance on the datum feature and smaller tolerances on the other considered features. However, it is technically correct and this approach was taken on this drawing to make a point. The parallelism is relative to the datum plane established by datum feature A not to datum …
